We propose to investigate the room-temperature excited-state properties of DNA and its analogs by steady-state and time- resolved fluorometry. We aim at establishing: 1. The occurrence and extent of migration of excitation energy along the double helix. 2. The degree of conformational flexibility of the double helix. 3. Ground- and excited-state interactions between the bases. 4. The pathways of deexcitation of the excited states. The proposed research will greatly enhance our knowledge of the structure and dynamics of nucleic acids and it will elucidate the primary events involved in their photodamage. We have already established the feasibility of several aspects of this research. This proposal requests support that will enable us to carry out a systematic investigation.